[BUG] Add missing API Spec Tests

[dblock]

What is the bug?

API specs test coverage using output added in #697.

• GET /
• HEAD /
• GET /_alias
• PUT /_alias
• GET /_alias/{name}
• HEAD /_alias/{name}
• POST /_alias/{name}
• PUT /_alias/{name}
• POST /_aliases
• POST /_aliases/{name}
• PUT /_aliases/{name}
• GET /_analyze
• POST /_analyze
• POST /_bulk
• PUT /_bulk
• POST /_bulk/stream
• PUT /_bulk/stream
• POST /_cache/clear
• GET /_cat
• GET /_cat/aliases
• GET /_cat/aliases/{name}
• GET /_cat/allocation
• GET /_cat/allocation/{node_id}
• GET /_cat/cluster_manager
• GET /_cat/count
• GET /_cat/count/{index}
• GET /_cat/fielddata
• GET /_cat/fielddata/{fields}
• GET /_cat/health
• GET /_cat/indices
• GET /_cat/indices/{index}
• GET /_cat/master
• GET /_cat/nodeattrs
• GET /_cat/nodes
• GET /_cat/pending_tasks
• GET /_cat/pit_segments
• GET /_cat/pit_segments/_all
• GET /_cat/plugins
• GET /_cat/recovery
• GET /_cat/recovery/{index}
• GET /_cat/repositories
• GET /_cat/segment_replication
• GET /_cat/segment_replication/{index}
• GET /_cat/segments
• GET /_cat/segments/{index}
• GET /_cat/shards
• GET /_cat/shards/{index}
• GET /_cat/snapshots
• GET /_cat/snapshots/{repository}
• GET /_cat/tasks
• GET /_cat/templates
• GET /_cat/templates/{name}
• GET /_cat/thread_pool
• GET /_cat/thread_pool/{thread_pool_patterns}
• GET /_cluster/allocation/explain
• POST /_cluster/allocation/explain
• DELETE /_cluster/decommission/awareness
• GET /_cluster/decommission/awareness/{awareness_attribute_name}/_status
• PUT /_cluster/decommission/awareness/{awareness_attribute_name}/{awareness_attribute_value}
• GET /_cluster/health
• GET /_cluster/health/{index}
• GET /_cluster/nodes/hot_threads
• GET /_cluster/nodes/{node_id}/hot_threads
• GET /_cluster/pending_tasks
• POST /_cluster/reroute
• DELETE /_cluster/routing/awareness/weights
• GET /_cluster/routing/awareness/{attribute}/weights
• PUT /_cluster/routing/awareness/{attribute}/weights
• GET /_cluster/settings
• PUT /_cluster/settings
• GET /_cluster/state
• GET /_cluster/state/{metric}
• GET /_cluster/state/{metric}/{index}
• GET /_cluster/stats
• GET /_cluster/stats/nodes/{node_id}
• GET /_cluster/stats/{metric}/nodes/{node_id}
• GET /_cluster/stats/{metric}/{index_metric}/nodes/{node_id}
• DELETE /_cluster/voting_config_exclusions
• POST /_cluster/voting_config_exclusions
• GET /_component_template
• DELETE /_component_template/{name}
• GET /_component_template/{name}
• HEAD /_component_template/{name}
• POST /_component_template/{name}
• PUT /_component_template/{name}
• GET /_count
• POST /_count
• GET /_dangling
• DELETE /_dangling/{index_uuid}
• POST /_dangling/{index_uuid}
• GET /_data_stream
• GET /_data_stream/_stats
• DELETE /_data_stream/{name}
• GET /_data_stream/{name}
• PUT /_data_stream/{name}
• GET /_data_stream/{name}/_stats
• POST /_delete_by_query/{task_id}/_rethrottle
• GET /_field_caps
• POST /_field_caps
• GET /_flush
• POST /_flush
• POST /_forcemerge
• GET /_index_template
• POST /_index_template/_simulate
• POST /_index_template/_simulate/{name}
• POST /_index_template/_simulate_index/{name}
• DELETE /_index_template/{name}
• GET /_index_template/{name}
• HEAD /_index_template/{name}
• POST /_index_template/{name}
• PUT /_index_template/{name}
• GET /_ingest/pipeline
• GET /_ingest/pipeline/_simulate
• POST /_ingest/pipeline/_simulate
• DELETE /_ingest/pipeline/{id}
• GET /_ingest/pipeline/{id}
• PUT /_ingest/pipeline/{id}
• GET /_ingest/pipeline/{id}/_simulate
• POST /_ingest/pipeline/{id}/_simulate
• GET /_ingest/processor/grok
• GET /_insights/top_queries
• GET /_list
• GET /_list/indices
• GET /_list/indices/{index}
• GET /_list/shards
• GET /_list/shards/{index}
• GET /_mapping
• GET /_mapping/field/{fields}
• GET /_mget
• POST /_mget
• GET /_msearch
• POST /_msearch
• GET /_msearch/template
• POST /_msearch/template
• GET /_mtermvectors
• POST /_mtermvectors
• GET /_nodes
• GET /_nodes/hot_threads
• POST /_nodes/reload_secure_settings
• GET /_nodes/stats
• GET /_nodes/stats/{metric}
• GET /_nodes/stats/{metric}/{index_metric}
• GET /_nodes/usage
• GET /_nodes/usage/{metric}
• GET /_nodes/{node_id_or_metric}
• GET /_nodes/{node_id}/hot_threads
• POST /_nodes/{node_id}/reload_secure_settings
• GET /_nodes/{node_id}/stats
• GET /_nodes/{node_id}/stats/{metric}
• GET /_nodes/{node_id}/stats/{metric}/{index_metric}
• GET /_nodes/{node_id}/usage
• GET /_nodes/{node_id}/usage/{metric}
• GET /_nodes/{node_id}/{metric}
• GET /_opendistro/_security/sslinfo
• POST /_plugins/_asynchronous_search
• GET /_plugins/_asynchronous_search/stats
• DELETE /_plugins/_asynchronous_search/{id}
• GET /_plugins/_asynchronous_search/{id}
• POST /_plugins/_flow_framework/workflow
• GET /_plugins/_flow_framework/workflow/_search
• POST /_plugins/_flow_framework/workflow/_search
• GET /_plugins/_flow_framework/workflow/_steps
• GET /_plugins/_flow_framework/workflow/state/_search
• POST /_plugins/_flow_framework/workflow/state/_search
• DELETE /_plugins/_flow_framework/workflow/{workflow_id}
• GET /_plugins/_flow_framework/workflow/{workflow_id}
• PUT /_plugins/_flow_framework/workflow/{workflow_id}
• POST /_plugins/_flow_framework/workflow/{workflow_id}/_deprovision
• POST /_plugins/_flow_framework/workflow/{workflow_id}/_provision
• GET /_plugins/_flow_framework/workflow/{workflow_id}/_status
• POST /_plugins/_ism/add
• POST /_plugins/_ism/add/{index}
• POST /_plugins/_ism/change_policy
• POST /_plugins/_ism/change_policy/{index}
• GET /_plugins/_ism/explain
• POST /_plugins/_ism/explain
• GET /_plugins/_ism/explain/{index}
• POST /_plugins/_ism/explain/{index}
• GET /_plugins/_ism/policies
• PUT /_plugins/_ism/policies
• DELETE /_plugins/_ism/policies/{policy_id}
• GET /_plugins/_ism/policies/{policy_id}
• HEAD /_plugins/_ism/policies/{policy_id}
• PUT /_plugins/_ism/policies/{policy_id}
• POST /_plugins/_ism/remove
• POST /_plugins/_ism/remove/{index}
• POST /_plugins/_ism/retry
• POST /_plugins/_ism/retry/{index}
• GET /_plugins/_knn/models/_search
• POST /_plugins/_knn/models/_search
• POST /_plugins/_knn/models/_train
• DELETE /_plugins/_knn/models/{model_id}
• GET /_plugins/_knn/models/{model_id}
• POST /_plugins/_knn/models/{model_id}/_train
• GET /_plugins/_knn/stats
• GET /_plugins/_knn/stats/{stat}
• GET /_plugins/_knn/warmup/{index}
• GET /_plugins/_knn/{node_id}/stats
• GET /_plugins/_knn/{node_id}/stats/{stat}
• POST /_plugins/_ml/agents/_register
• DELETE /_plugins/_ml/agents/{agent_id}
• POST /_plugins/_ml/connectors/_create
• DELETE /_plugins/_ml/connectors/{connector_id}
• POST /_plugins/_ml/model_groups/_register
• DELETE /_plugins/_ml/model_groups/{model_group_id}
• GET /_plugins/_ml/model_groups/{model_group_id}
• POST /_plugins/_ml/models/_register
• GET /_plugins/_ml/models/_search
• DELETE /_plugins/_ml/models/{model_id}
• POST /_plugins/_ml/models/{model_id}/_deploy
• POST /_plugins/_ml/models/{model_id}/_undeploy
• DELETE /_plugins/_ml/tasks/{task_id}
• GET /_plugins/_ml/tasks/{task_id}
• GET /_plugins/_notifications/channels
• DELETE /_plugins/_notifications/configs
• GET /_plugins/_notifications/configs
• POST /_plugins/_notifications/configs
• DELETE /_plugins/_notifications/configs/{config_id}
• GET /_plugins/_notifications/configs/{config_id}
• PUT /_plugins/_notifications/configs/{config_id}
• GET /_plugins/_notifications/feature/test/{config_id}
• POST /_plugins/_notifications/feature/test/{config_id}
• GET /_plugins/_notifications/features
• GET /_plugins/_observability/_local/stats
• DELETE /_plugins/_observability/object
• GET /_plugins/_observability/object
• POST /_plugins/_observability/object
• DELETE /_plugins/_observability/object/{object_id}
• GET /_plugins/_observability/object/{object_id}
• PUT /_plugins/_observability/object/{object_id}
• POST /_plugins/_ppl
• POST /_plugins/_ppl/_explain
• GET /_plugins/_ppl/stats
• POST /_plugins/_ppl/stats
• GET /_plugins/_query/_datasources
• POST /_plugins/_query/_datasources
• PUT /_plugins/_query/_datasources
• DELETE /_plugins/_query/_datasources/{datasource_name}
• GET /_plugins/_query/_datasources/{datasource_name}
• PUT /_plugins/_query/settings
• POST /_plugins/_refresh_search_analyzers/{index}
• DELETE /_plugins/_replication/_autofollow
• POST /_plugins/_replication/_autofollow
• GET /_plugins/_replication/autofollow_stats
• GET /_plugins/_replication/follower_stats
• GET /_plugins/_replication/leader_stats
• POST /_plugins/_replication/{index}/_pause
• POST /_plugins/_replication/{index}/_resume
• PUT /_plugins/_replication/{index}/_start
• GET /_plugins/_replication/{index}/_status
• POST /_plugins/_replication/{index}/_stop
• PUT /_plugins/_replication/{index}/_update
• DELETE /_plugins/_rollup/jobs/{id}
• GET /_plugins/_rollup/jobs/{id}
• PUT /_plugins/_rollup/jobs/{id}
• GET /_plugins/_rollup/jobs/{id}/_explain
• POST /_plugins/_rollup/jobs/{id}/_start
• POST /_plugins/_rollup/jobs/{id}/_stop
• GET /_plugins/_security/api/_upgrade_check
• POST /_plugins/_security/api/_upgrade_perform
• GET /_plugins/_security/api/account
• PUT /_plugins/_security/api/account
• GET /_plugins/_security/api/actiongroups
• PATCH /_plugins/_security/api/actiongroups
• DELETE /_plugins/_security/api/actiongroups/{action_group}
• GET /_plugins/_security/api/actiongroups/{action_group}
• PATCH /_plugins/_security/api/actiongroups/{action_group}
• PUT /_plugins/_security/api/actiongroups/{action_group}
• GET /_plugins/_security/api/allowlist
• PATCH /_plugins/_security/api/allowlist
• PUT /_plugins/_security/api/allowlist
• GET /_plugins/_security/api/audit
• PATCH /_plugins/_security/api/audit
• PUT /_plugins/_security/api/audit/config
• POST /_plugins/_security/api/authtoken
• DELETE /_plugins/_security/api/cache
• GET /_plugins/_security/api/cache
• POST /_plugins/_security/api/cache
• PUT /_plugins/_security/api/cache
• GET /_plugins/_security/api/certificates
• GET /_plugins/_security/api/certificates/{node_id}
• POST /_plugins/_security/api/generateonbehalfoftoken
• GET /_plugins/_security/api/internalusers
• PATCH /_plugins/_security/api/internalusers
• DELETE /_plugins/_security/api/internalusers/{username}
• GET /_plugins/_security/api/internalusers/{username}
• PATCH /_plugins/_security/api/internalusers/{username}
• PUT /_plugins/_security/api/internalusers/{username}
• POST /_plugins/_security/api/internalusers/{username}/authtoken
• POST /_plugins/_security/api/migrate
• GET /_plugins/_security/api/nodesdn
• PATCH /_plugins/_security/api/nodesdn
• DELETE /_plugins/_security/api/nodesdn/{cluster_name}
• GET /_plugins/_security/api/nodesdn/{cluster_name}
• PATCH /_plugins/_security/api/nodesdn/{cluster_name}
• PUT /_plugins/_security/api/nodesdn/{cluster_name}
• GET /_plugins/_security/api/permissionsinfo
• GET /_plugins/_security/api/roles
• PATCH /_plugins/_security/api/roles
• DELETE /_plugins/_security/api/roles/{role}
• GET /_plugins/_security/api/roles/{role}
• PATCH /_plugins/_security/api/roles/{role}
• PUT /_plugins/_security/api/roles/{role}
• GET /_plugins/_security/api/rolesmapping
• PATCH /_plugins/_security/api/rolesmapping
• DELETE /_plugins/_security/api/rolesmapping/{role}
• GET /_plugins/_security/api/rolesmapping/{role}
• PATCH /_plugins/_security/api/rolesmapping/{role}
• PUT /_plugins/_security/api/rolesmapping/{role}
• GET /_plugins/_security/api/securityconfig
• PATCH /_plugins/_security/api/securityconfig
• PUT /_plugins/_security/api/securityconfig/config
• GET /_plugins/_security/api/ssl/certs
• PUT /_plugins/_security/api/ssl/http/reloadcerts
• PUT /_plugins/_security/api/ssl/transport/reloadcerts
• GET /_plugins/_security/api/tenancy/config
• PUT /_plugins/_security/api/tenancy/config
• GET /_plugins/_security/api/tenants
• PATCH /_plugins/_security/api/tenants
• DELETE /_plugins/_security/api/tenants/{tenant}
• GET /_plugins/_security/api/tenants/{tenant}
• PATCH /_plugins/_security/api/tenants/{tenant}
• PUT /_plugins/_security/api/tenants/{tenant}
• GET /_plugins/_security/api/user
• DELETE /_plugins/_security/api/user/{username}
• GET /_plugins/_security/api/user/{username}
• PUT /_plugins/_security/api/user/{username}
• POST /_plugins/_security/api/user/{username}/authtoken
• GET /_plugins/_security/api/validate
• GET /_plugins/_security/authinfo
• POST /_plugins/_security/authinfo
• GET /_plugins/_security/dashboardsinfo
• POST /_plugins/_security/dashboardsinfo
• GET /_plugins/_security/health
• POST /_plugins/_security/health
• GET /_plugins/_security/tenantinfo
• POST /_plugins/_security/tenantinfo
• GET /_plugins/_security/whoami
• POST /_plugins/_security/whoami
• GET /_plugins/_security/whoamiprotected
• GET /_plugins/_sm/policies
• DELETE /_plugins/_sm/policies/{policy_name}
• GET /_plugins/_sm/policies/{policy_name}
• POST /_plugins/_sm/policies/{policy_name}
• PUT /_plugins/_sm/policies/{policy_name}
• GET /_plugins/_sm/policies/{policy_name}/_explain
• POST /_plugins/_sm/policies/{policy_name}/_start
• POST /_plugins/_sm/policies/{policy_name}/_stop
• POST /_plugins/_sql
• POST /_plugins/_sql/_explain
• POST /_plugins/_sql/close
• GET /_plugins/_sql/stats
• POST /_plugins/_sql/stats
• GET /_plugins/_transform
• POST /_plugins/_transform/_preview
• DELETE /_plugins/_transform/{id}
• GET /_plugins/_transform/{id}
• PUT /_plugins/_transform/{id}
• GET /_plugins/_transform/{id}/_explain
• POST /_plugins/_transform/{id}/_start
• POST /_plugins/_transform/{id}/_stop
• GET /_rank_eval
• POST /_rank_eval
• GET /_recovery
• GET /_refresh
• POST /_refresh
• POST /_reindex
• POST /_reindex/{task_id}/_rethrottle
• GET /_remote/info
• POST /_remotestore/_restore
• GET /_render/template
• POST /_render/template
• GET /_render/template/{id}
• POST /_render/template/{id}
• GET /_resolve/index/{name}
• GET /_script_context
• GET /_script_language
• GET /_scripts/painless/_execute
• POST /_scripts/painless/_execute
• DELETE /_scripts/{id}
• GET /_scripts/{id}
• POST /_scripts/{id}
• PUT /_scripts/{id}
• POST /_scripts/{id}/{context}
• PUT /_scripts/{id}/{context}
• GET /_search
• POST /_search
• GET /_search/pipeline
• DELETE /_search/pipeline/{id}
• GET /_search/pipeline/{id}
• PUT /_search/pipeline/{id}
• DELETE /_search/point_in_time
• DELETE /_search/point_in_time/_all
• GET /_search/point_in_time/_all
• DELETE /_search/scroll
• GET /_search/scroll
• POST /_search/scroll
• DELETE /_search/scroll/{scroll_id}
• GET /_search/scroll/{scroll_id}
• POST /_search/scroll/{scroll_id}
• GET /_search/template
• POST /_search/template
• GET /_search_shards
• POST /_search_shards
• GET /_segments
• GET /_settings
• PUT /_settings
• GET /_settings/{name}
• GET /_shard_stores
• GET /_snapshot
• GET /_snapshot/_status
• DELETE /_snapshot/{repository}
• GET /_snapshot/{repository}
• POST /_snapshot/{repository}
• PUT /_snapshot/{repository}
• POST /_snapshot/{repository}/_cleanup
• GET /_snapshot/{repository}/_status
• POST /_snapshot/{repository}/_verify
• DELETE /_snapshot/{repository}/{snapshot}
• GET /_snapshot/{repository}/{snapshot}
• POST /_snapshot/{repository}/{snapshot}
• PUT /_snapshot/{repository}/{snapshot}
• PUT /_snapshot/{repository}/{snapshot}/_clone/{target_snapshot}
• POST /_snapshot/{repository}/{snapshot}/_restore
• GET /_snapshot/{repository}/{snapshot}/_status
• GET /_stats
• GET /_stats/{metric}
• GET /_tasks
• POST /_tasks/_cancel
• GET /_tasks/{task_id}
• POST /_tasks/{task_id}/_cancel
• GET /_template
• DELETE /_template/{name}
• GET /_template/{name}
• HEAD /_template/{name}
• POST /_template/{name}
• PUT /_template/{name}
• POST /_update_by_query/{task_id}/_rethrottle
• GET /_upgrade
• POST /_upgrade
• GET /_validate/query
• POST /_validate/query
• GET /_wlm/query_group
• PUT /_wlm/query_group
• DELETE /_wlm/query_group/{name}
• GET /_wlm/query_group/{name}
• PUT /_wlm/query_group/{name}
• POST /{alias}/_rollover
• POST /{alias}/_rollover/{new_index}
• DELETE /{index}
• GET /{index}
• HEAD /{index}
• PUT /{index}
• GET /{index}/_alias
• PUT /{index}/_alias
• DELETE /{index}/_alias/{name}
• GET /{index}/_alias/{name}
• HEAD /{index}/_alias/{name}
• POST /{index}/_alias/{name}
• PUT /{index}/_alias/{name}
• PUT /{index}/_aliases
• DELETE /{index}/_aliases/{name}
• POST /{index}/_aliases/{name}
• PUT /{index}/_aliases/{name}
• GET /{index}/_analyze
• POST /{index}/_analyze
• PUT /{index}/_block/{block}
• POST /{index}/_bulk
• PUT /{index}/_bulk
• POST /{index}/_bulk/stream
• PUT /{index}/_bulk/stream
• POST /{index}/_cache/clear
• POST /{index}/_clone/{target}
• PUT /{index}/_clone/{target}
• POST /{index}/_close
• GET /{index}/_count
• POST /{index}/_count
• POST /{index}/_create/{id}
• PUT /{index}/_create/{id}
• POST /{index}/_delete_by_query
• POST /{index}/_doc
• DELETE /{index}/_doc/{id}
• GET /{index}/_doc/{id}
• HEAD /{index}/_doc/{id}
• POST /{index}/_doc/{id}
• PUT /{index}/_doc/{id}
• GET /{index}/_explain/{id}
• POST /{index}/_explain/{id}
• GET /{index}/_field_caps
• POST /{index}/_field_caps
• GET /{index}/_flush
• POST /{index}/_flush
• POST /{index}/_forcemerge
• GET /{index}/_mapping
• POST /{index}/_mapping
• PUT /{index}/_mapping
• GET /{index}/_mapping/field/{fields}
• GET /{index}/_mget
• POST /{index}/_mget
• GET /{index}/_msearch
• POST /{index}/_msearch
• GET /{index}/_msearch/template
• POST /{index}/_msearch/template
• GET /{index}/_mtermvectors
• POST /{index}/_mtermvectors
• POST /{index}/_open
• GET /{index}/_rank_eval
• POST /{index}/_rank_eval
• GET /{index}/_recovery
• GET /{index}/_refresh
• POST /{index}/_refresh
• GET /{index}/_search
• POST /{index}/_search
• POST /{index}/_search/point_in_time
• GET /{index}/_search/template
• POST /{index}/_search/template
• GET /{index}/_search_shards
• POST /{index}/_search_shards
• GET /{index}/_segments
• GET /{index}/_settings
• PUT /{index}/_settings
• GET /{index}/_settings/{name}
• GET /{index}/_shard_stores
• POST /{index}/_shrink/{target}
• PUT /{index}/_shrink/{target}
• GET /{index}/_source/{id}
• HEAD /{index}/_source/{id}
• POST /{index}/_split/{target}
• PUT /{index}/_split/{target}
• GET /{index}/_stats
• GET /{index}/_stats/{metric}
• GET /{index}/_termvectors
• POST /{index}/_termvectors
• GET /{index}/_termvectors/{id}
• POST /{index}/_termvectors/{id}
• POST /{index}/_update/{id}
• POST /{index}/_update_by_query
• GET /{index}/_upgrade
• POST /{index}/_upgrade
• GET /{index}/_validate/query
• POST /{index}/_validate/query

What is the expected behavior?

100% test coverage.

Do you have any additional context?

1. Read https://github.com/opensearch-project/opensearch-api-specification/blob/main/TESTING_GUIDE.md.
2. Pick a test from the list to add. Every PR will have a step called "merge test coverage" that will show missing ones, example.

[Tokesh]

Hello! I would like to work with index APIs

[dblock]

@Tokesh I did _explain in #685. Take the rest!